[cleanup] CSA: add helpers for accessing details/value via key_index

src/heap/mark-compact.cc

Index: src/heap/mark-compact.cc
diff --git a/src/heap/mark-compact.cc b/src/heap/mark-compact.cc
index 78db331ef07462506d5f4e565b40e03e5ecb1e91..ced0172d0bcf636f695270fbaa401c6ad8962483 100644
--- a/src/heap/mark-compact.cc
+++ b/src/heap/mark-compact.cc
@@ -2708,7 +2708,7 @@ void MarkCompactCollector::TrimDescriptorArray(Map* map,
   int to_trim = number_of_descriptors - number_of_own_descriptors;
   if (to_trim > 0) {
     heap_->RightTrimFixedArray(descriptors,
-                               to_trim * DescriptorArray::kDescriptorSize);
+                               to_trim * DescriptorArray::kEntrySize);
     descriptors->SetNumberOfDescriptors(number_of_own_descriptors);
 
     if (descriptors->HasEnumCache()) TrimEnumCache(map, descriptors);